Principle of stepper direct acting solenoid valve: It is a combination of direct acting and pilot operated principles. When there is no pressure difference between the inlet and outlet, the electromagnetic force directly lifts the pilot small valve and the main valve closure part upwards after being energized, and the valve opens. When the inlet and outlet reach the starting pressure difference, after being energized, the electromagnetic force will pilot the small valve. The pressure in the lower chamber of the main valve will increase, and the pressure in the upper chamber will decrease. The main valve will be pushed upwards by the pressure difference. When the power is cut off, the pilot valve pushes the closing component through spring force or medium pressure and moves downwards to close the valve.